It’s a well-known factoid that batteries keep getting cheaper while capacity increases. That said, as with any market that is full of people who are hunting for that ‘great deal’, there are also many shady sellers who will happily sell you a product that could be very dangerous. Especially in the case of large LiFePO4 (LFP) batteries, considering the sheer amount of energy they can contain. Recently [Will Prowse] nabbed such a $125, 100 Ah battery off Amazon that carries no recognizable manufacturer or brand name.
If this battery works well, it could be an amazing deal for off-grid and solar-powered applications. Running a battery of tests on the battery, [Will] found that the unit’s BMS featured no over-current protection, happily surging to 400 A, with only over-temperature protection keeping it from melting down during a discharge scenario. Interestingly, under-temperature charge protection also worked on the unit.
After a (safe) teardown of the battery the real discoveries began, with a row of missing cells, the other cells being re-sleeved and thus likely salvaged or rejects. Fascinatingly, another YouTuber did a similar test and found that their (even cheaper) unit was of a much lower capacity (88.9 Ah) than [Will]’s with 98 Ah and featured a completely different BMS to boot. Their unit did however feature something of a brand name, though it’s much more likely that these are all just generic LFP batteries that get re-branded by resellers.
What this means is that these LFP batteries may be cheap, but they come with cells that are likely to be of questionable quality, featuring a BMS that plays it fast and loose with safety. Although [Will] doesn’t outright say that you shouldn’t use these batteries, he does recommend that you install a fuse on it to provide some semblance of over-current protection. Keeping a fire extinguisher at hand might also be a good idea.
I mean, if you have a garden, you could dig a pit, concrete-line it and place all that stuff into it.
Totally secure.
You mean, move it straight to landfill? That’s pretty much the best thing to do with a lot of the garbage that Amazon ships nowadays, from vendors with names that look like a cat walked over a keyboard. “Hmm shall I buy the battery pack from JOUTKFR or from TUJNWOO? Both have identical pricing and product photography but the former has dozens of 5* reviews saying it’s a great box of disposable rubber gloves…”
That’s going to be a problem when it rains. Additional measure will need to be taken.
A good clear fire exit is going to be a lot more likely to save you than a fire extingusher if one of these large batteries goes up in flames. I mean a fire extinguisher is always a good idea, but I wouldn’t count on it for a lithium fire. Better to chuck a fire blanket over the battery, run for it and call the fire brigade.
I would suggest building and housing the batteries in small above-ground outdoor structure that is at least a few meters away. A modified water-tight case with buried conduit may be sufficient.
Don’t LiFePO4’s tend to light on fire a lot less? Like that’s why BYD can compensate for the lower power density with banks of prismatic cells?
Lifepo4 is less likely to burn, but not by much. Lion as used by the bicycle and scooter people, whole different story.
and that’s assuming these are really lifepo4…
The voltage is different so it’s hard to disguise any other battery type as lifepo4.
If you want less-fire-prone or easier-to-put-out-a-fire batteries, at least consider non-Lithium solutions. Sure, they make take up more room and may have more mass, but if it’s for your off-grid shack out in the boondocks or even your house, the space-vs-safety trade-off may be worth it.
THis is a timely article. I’m considering replacing my dad’s wheelchair AGMs with LiFePo4 equivalents…
For safety and reliability reasons, I would suggest looking into sodium-ion cells. Cheap LiFePo4 batteries generally have a poor reliability. They are a bit more expensive and only medium density but a single mishap is more costly.
There may be better ones but here’s a sodium-ion cell: https://www.motawillbattery.com/26700-sodium-ion-battery-3-1v-3300mah-na-ion-cell/ (note the 10 year warranty)
As an SWL/CBer who eventually wants to try out 12v lead-gel accu alternatives,
I’d rather get some Emerit rechargeables from here in Germany.
According to the website they’re offering LiFePO4 accus with UN38.3/IEC62133 certification and a warranty.
Better safe than sorry. Such high-power-density batteries are like dynamite.